Electrolyte Materials for Batteries and Methods for Use

ABSTRACT

An electrolyte solution comprising an additive wherein the additive is not substantially consumed during charge and discharge cycles of the electrochemical cell. Additives include Lewis acids, electron-rich transition metal complexes, and electron deficient pi-conjugated systems.

This application is a Continuation of and claims the benefit of priorityto pending U.S. Non-provisional application Ser. No. 13/612,798 filedSep. 12, 2012 entitled “Electrolyte Materials for Batteries and Methodsfor Use”, which claims the benefit of priority to U.S. ProvisionalApplication No. 61/533,906 filed Sep. 13, 2011 entitled “Carbon-FluorideBattery”. Both the '798 and '906 applications are incorporated herein byreference in their entirety.

BACKGROUND OF THE INVENTION

The present invention is in the field of battery technology, and moreparticularly in the area of using additives to enhance electrolyte andelectrode performance in metal-fluoride and carbon-fluoride batteries.

One type of battery consists of a negative electrode made primarily fromlithium and a positive electrode made primarily from a compoundcontaining carbon and fluorine. These batteries can be referred to aslithium/carbon-fluoride batteries or Li—CF batteries.

Lithium/carbon-fluoride batteries are used extensively in medicalapplication, as back-up power electronics, military applications, and inother settings. Lithium/carbon-fluoride batteries have the highestspecific energy of any batteries currently commercially available.

During discharge, lithium ions and electrons are generated fromoxidation of the negative electrode while fluoride ions and carbon orproduced from reduction of the positive electrode. The generatedfluoride ions react with lithium ions near the positive electrode toproduce a compound containing lithium and fluorine, which may deposit atthe positive electrode surface.

Lithium/carbon-fluoride batteries enjoyed widespread use in commercialapplications in part due to certain desirable characteristics. Thecarbon-fluoride positive electrode is lightweight, which makes thebattery desirable in portable or mobile applications where weight is animportant design consideration. Also, the carbon-fluoride positiveelectrode has a high capacity. Further, the overall reaction has a highelectrochemical potential.

Despite their widespread use, lithium/carbon-fluoride batteries sufferfrom certain challenges.

The carbon-fluoride compound and the lithium-fluoride compound havecomparatively low electrical conductivity as compared to certain otherbattery materials. Such comparatively low electrical conductivity canhave the following results in electrochemical cell: comparatively lowpower; comparatively low operating voltage; comparatively largeunderpotential upon discharge; and the comparatively low capacity duringa high rate of discharge.

The carbon-fluoride compound and the lithium-fluoride compound havecomparatively low thermal conductivity as compared to certain otherbattery materials and such comparatively low thermal conductivity canresult in comparatively significant heat generation by theelectrochemical cell upon discharge.

Breaking the carbon-fluoride bonds of the carbon-fluoride compoundrequires a comparatively high activation energy as compared to certainother battery materials. Such comparatively high activation energy forbond breaking can have the following results and electrochemical cell:comparatively low power; comparatively low operating voltage;comparatively large under potential upon discharge; comparatively lowcapacity during a high rate of discharge; and comparatively significantheat generation upon discharge.

Metal-fluoride batteries have many of the same problems. Additionally,rechargeable metal-fluoride batteries have a large overpotential duringcharging, resulting in a poor energy efficiency.

There have been prior attempts to address such challenges. One priorattempt involves forming a composite positive electrode. The rawcomposite material contains a carbon-fluoride compound and a secondcompound, which is comparatively more electrically conductive than thecarbon-fluoride compound. These two compounds are mixed together to forma composite material that is then formed into a positive electrode.

One example of such composite material is a carbon-fluoride compoundcomposited with silver vanadium oxide (silver vanadium oxide is oftenabbreviated as “SVO” in the battery industry rather than by its periodictable symbols). This CFx/SVO composite material has been used to form apositive electrode and a battery for use in medical devices and hasdemonstrated increased pulse power and increased energy density whencompared to a battery using a positive electrode formed only fromcarbon-fluoride.

CFx/SVO composite or hybrid cathode materials can exhibit high energyand high pulse power. However, in batteries using CFx/SVO hybrid cathodematerials, power can degrade below critical limits for particulardevices at a late depth of discharge.

Another example of a composite material for use in forming a positiveelectrode is a carbon-fluoride compound composited with manganesedioxide (MnO₂). This CF/MnO₂ composite material has been used to form apositive electrode where cost is a key design factor and hasdemonstrated increased power at high discharge rates, increased energydensity, and reduced heat buildup in the electrochemical cell whencompared to a battery using a positive electrode formed only fromcarbon-fluoride.

Although prior batteries using positive electrodes formed from these andcertain other composite materials generally have higher power, higheroperating potential, lower under potential, and less heat build up whencompared to batteries using a positive electrode formed only frommetal-fluoride or carbon-fluoride, the performance of electrochemicalcell could be improved significantly. Also, certain of these performanceimprovements come at the expense of reduced energy density.

Certain embodiments of the present invention address the challengesfound in batteries. Certain embodiments of the present invention can beused to form electrochemical cells for batteries that exhibit lowerunder potential, higher power, higher capacity at a high discharge rate,less heat generation, or faster heat dissipation when compared to priorbatteries.

These and other challenges can be addressed by embodiments of thepresent invention described below.

BRIEF SUMMARY OF THE INVENTION

Certain embodiments of the invention include an electrochemical cellhaving a positive electrode, a negative electrode, and an electrolytesolution. In certain embodiments the positive electrode is formed from afirst fluoride compound and produces a second fluoride compound upondischarge. In certain embodiments the electrolyte solution includes anadditive in which the additive includes a ligand and a central atom.Certain embodiments of the invention include all of these features.

In certain embodiments, the additive is not substantially consumedduring charge and discharge cycles of the electrochemical cell. Incertain embodiments, the additive comprises an electron-rich transitionmetal complex.

In certain embodiments of the invention, the additive is mixed with anelectrolyte solution. In certain embodiments of the invention, theadditive is at least partially dissolved in the electrolyte solution. Incertain embodiments of the invention the additive is mixed with theelectrolyte solution at a non-stoichiometric ratio of additive to thefirst fluoride compound.

In certain embodiments of the invention, the additive at least partiallysolubilizes the second fluoride compound in the electrolyte solution. Incertain embodiments of the invention, the additive catalyzes thebreakage of chemical bonds in the first fluoride compound. In certainembodiments of the invention, the additive reversibly coordinatesfluoride ions. In certain embodiments of the invention, the additivereduces the formation of aggregates of the second fluoride compound.Certain embodiments of the invention include all of these features.

In certain embodiments of the invention, the additive includes a Lewisacid. In certain embodiments of the invention, the additive includes analkali central atom, an alkaline earth central atom, a transition metalcentral atom, a rare earth central atom, a late transition metal centralatom, a metalloid central atom, or combinations of such central atoms.In certain embodiments of the invention, the ligand is electronwithdrawing. In certain embodiments of the invention, the ligand iselectron donating.

Certain embodiments include the method of making an electrolyte solutioncontaining novel additives, the method of making an electrochemical cellcontaining electrolyte solutions with novel additives, and methods ofuse of such electrochemical cells.

BRIEF DESCRIPTION OF SEVERAL VIEWS OF THE DRAWINGS

FIGS. 1A and 1B depict the results of testing of an electrolyte solutioncontaining various additives according to certain embodiments of theinvention in an electrochemical cell as compared to control. Certainadditives demonstrate improved voltage performance.

FIG. 2 depicts the results of testing of an electrolyte solutioncontaining various additives according to certain embodiments of theinvention in an electrochemical cell as compared to control. Certainadditives demonstrate improved pulse power performance.

FIG. 3 depicts the results of testing of an electrolyte solutioncontaining various additives according to certain embodiments of theinvention in an electrochemical cell as compared to control. Certainadditives demonstrate improved pulse power performance.

FIG. 4 depicts the results of testing of an electrolyte solutioncontaining an additive according to certain embodiments of the inventionin an electrochemical cell as compared to control. The additivedemonstrates improved pulse power performance at varying depths ofdischarge.

FIG. 5 depicts the results of testing of an electrolyte solutioncontaining an additive according to certain embodiments of the inventionin an electrochemical cell as compared to control. The additivedemonstrates improved voltage performance.

FIG. 6 depicts the results of testing of an electrolyte solutioncontaining an additive according to certain embodiments of the inventionin an electrochemical cell as compared to control. The additivedemonstrates improved voltage performance.

FIG. 7 depicts the results of testing of an electrolyte solutioncontaining an additive according to certain embodiments of the inventionin an electrochemical cell as compared to control. The additivedemonstrates improved voltage performance as a function of capacity.

DETAILED DESCRIPTION OF THE INVENTION

The following definitions apply to some of the aspects described withrespect to some embodiments of the invention. These definitions maylikewise be expanded upon herein. Each term is further explained andexemplified throughout the description, figures, and examples. Anyinterpretation of the terms in this description should take into accountthe full description, figures, and examples presented herein.

The singular terms “a”, “an”, and “the” include the plural unless thecontext clearly dictates otherwise. Thus, for example, reference to anobject can include multiple objects unless the context clearly dictatesotherwise.

The terms “substantially” and “substantial” refer to a considerabledegree or extent. When used in conjunction with an event orcircumstance, the terms can refer to instances in which the event orcircumstance occurs precisely as well as instances in which the event orcircumstance occurs to a close approximation, such as accounting fortypical tolerance levels or variability of the embodiments describedherein.

The term “about” refers to the range of values approximately near thegiven value in order to account for typical tolerance levels,measurement precision, or other variability of the embodiments describedherein.

The term “atom” refers to atoms in charged states as well as in aneutral state.

The term “compound” refers to atomic and molecular species that arechemically bound as well as materials that are physically mixed orbound, and such differences in meaning can be determined by the contextof the usage.

The term “ion” refers to charged atomic and molecular species.

The term “chemical bond” includes covalent, Ionic, and othercoordinating bonds between or among atomic or molecular species.

The term “alkali” refers to any of the chemical element in group 1 ofthe periodic table, including lithium (Li), sodium (Na), potassium (K),rubidium (Rb), cesium (Cs), and francium (Fr).

The term “alkaline earth” refers to any of the chemical elements ingroup 2 of the periodic table, including beryllium (Be), magnesium (Mg),calcium (Ca), strontium (Sr), barium (Ba), and radium (Ra).

The term “rare earth” refers to scandium (Sc), yttrium (Y), lanthanum(La), cerium (Ce), praseodymium (Pr), neodymium (Nd), promethium (Pm),samarium (Sm), europium (Eu), gadolinium (Gd), terbium (Tb), dysprosium(Dy), holmium (Ho), erbium (Er), thulium (Tm), ytterbium (Yb), andlutetium (Lu).

The term “metalloid” refers to a chemical element with properties thatare in-between or a mixture of those of metals and nonmetals, includingboron (B), silicon (Si), germanium (Ge), arsenic (As), antimony (Sb),tellurium (Te), carbon (C), aluminum (Al), selenium (Se), polonium (Po),and astatine (At).

The term “transition metal” refers to a chemical element in groups 3through 12 of the periodic table, including scandium (Sc), titanium(Ti), vanadium (V), chromium (Cr), manganese (Mn), iron (Fe), cobalt(Co), nickel (Ni), copper (Cu), zinc (Zn), yttrium (Y), zirconium (Zr),niobium (Nb), molybdenum (Mo), technetium (Tc), ruthenium (Ru), rhodium(Rh), palladium (Pd), silver (Ag), cadmium (Cd), hafnium (Hf), tantalum(Ta), tungsten (W), rhenium (Re), osmium (Os), iridium (Ir), platinum(Pt), gold (Au), mercury (Hg), rutherfordium (Rf), dubnium (Db),seaborgium (Sg), bohrium (Bh), hassium (Hs), and meitnerium (Mt).

A rate “C” refers to either (depending on context) the discharge currentas a fraction or multiple relative to a “1 C” current value under whicha battery (in a substantially fully charged state) would substantiallyfully discharge in one hour, or the charge current as a fraction ormultiple relative to a “1 C” current value under which the battery (in asubstantially fully discharged state) would substantially fully chargein one hour.

To the extent certain battery characteristics can vary with temperature,such characteristics are specified at room temperature (25° C.), unlessthe context clearly dictates otherwise.

Ranges presented herein are inclusive of their endpoints. Thus, forexample, the range 1 to 3 includes the values 1 and 3 as well as theintermediate values.

In certain embodiments, the electrolyte solution of electrochemical cellincludes an additive. These additives are useful in electrochemicalcells containing a metal-fluoride electrode. These additives are usefulelectrochemical cells containing a carbon-fluoride electrode. Theseadditives are useful in electrochemical cells containing an electrodeformed from a compound including a transition metal and fluorine. Such atransition metal in fluorine compounds include, but are not limited to,iron-fluoride compounds (such as FeF₃), manganese-fluoride compounds(such as MnF₃), nickel-fluoride (such as NiF₂), and copper-fluoridecompounds (such as CuF₂).

According to certain embodiments of the invention, one usefulcharacteristic of the additives is that they reversibly coordinatefluoride ions. Lewis acids are one type of compound that coordinatesfluoride ions. In certain embodiments of the invention, the additiveincludes a Lewis acid compound that coordinates fluoride ions, and inparticular the additive includes a Lewis acid compound that reversiblycoordinates fluoride ions. Certain additives include compounds formedfrom at least one ligand and at least one central atom. Theseligand/central atom compounds can be Lewis acids.

According to certain embodiments of the invention, appropriate ligandsinclude compounds capable of forming a Lewis acid when bound to centralatoms. Appropriate ligands can interact with the central atom in avariety of ways. For example, in certain embodiments ligands areelectron withdrawing while in other embodiments ligands are electrondonating. In certain embodiments, ligands exhibit steric effects ininteracting with the central atom. The specific characteristics of theligand affect how strongly or reversibly the additive coordinatesfluoride ions and can limit any side reactions that would cause theadditive to decompose.

According to certain embodiments of the invention, appropriate centralatoms include atoms capable of forming a Lewis acid with a ligand.According to certain aspects of the invention, appropriate central atomsare electron deficient and capable of coordinating fluoride ions.Central atoms can be alkali atoms, alkaline earth atoms, transitionmetal atoms, rare earth atoms, metalloids, or combinations of such atomtypes. According to certain embodiments of the invention, latetransition metal atoms are useful as central atoms. According to certainembodiments of the invention, atoms such as boron, aluminum (including3-coordinate aluminum), and antimony are useful as central atoms.

According to certain embodiments of the invention, another usefulcharacteristic of the additives is that they catalyze theelectrochemical breakage of carbon-fluorine bonds. Electron-richtransition metal catalysts are one class of additive that can catalyzethe electrochemical breakage of carbon-fluorine bonds. Suchelectron-rich transition metal catalysts have been used to fluorinateand/or defluorinate organic molecules.

Without being bound by a particular principal, hypothesis, or method ofaction not present in the claims, in addition to being an effectivecatalyst for breaking of carbon-fluorine bonds, materials according tocertain embodiments also: do not react with lithium metal or carbonfluoride when in the battery is in a resting state; react rapidly withlithium cations when in the oxidized state (preferably, the reactionoccurs more rapidly than diffusion to, and reaction with, the lithiumanode); and/or react with carbon fluoride via electrochemical reactionto reduce carbon fluoride or electron transfer from the carbon fluorideelectrode (or current collector) followed by chemical reaction withcarbon fluoride.

According to certain embodiments, some transition metal catalystsexhibit some of all of the characteristics describe above. For example,certain electron-rich transition metal complexes catalyzecarbon-fluorine bond activation. According to certain embodiments,electron-rich complexes including transition metals can exhibit thecharacteristics described above. According to certain embodiments,materials with electron deficient pi-conjugated systems can exhibit thecharacteristics described above. Examples of electron deficientpi-conjugated systems include, but are not limited to, benzene,1,3,5-trifluorobenzene, 1,3-dinitrobenzene, and2,3,5,6-tetrafluoro-7,7,8,8-tetracyanoquinodimethane.

As is demonstrated in the example and results disclosed herein,batteries fabricated from such additives that catalyze theelectrochemical breakage of carbon-fluorine bonds show significantlyhigher power (particularly at late depth of discharge) compared controlbatteries. Further, such additives that catalyze the electrochemicalbreakage of carbon-fluorine bonds provide improved power for the hybridcathode system as well as increased voltage for the pure CFx electrode.

According to certain embodiments of the invention, the additive is mixedwith a lithium salt that is useful in an electrolyte solution for anelectrochemical cell having a positive electrode formed from ametal-fluoride compound or a carbon-fluoride compound. For example,lithium salts useful in such an electrolyte solution include LiAsF₆,LiPF₆, LiBF₆, LiCl₄, and combinations thereof.

Without being bound by a particular principal, hypothesis, or method ofaction not present in the claims, certain embodiments of the inventioninclude additives that: reversibly coordinate fluoride ions to catalyzethe electrochemical breaking of metal-fluoride for carbon-fluoridechemical bonds; of lithium-fluoride compounds; reversibly coordinatefluoride ions to increase the mobility of lithium-fluoride compounds;reduce the formation of large aggregates on or within the pores of thepositive electrode; and/or aid the solvation and distribution ofinsulating LiF product.

According to certain embodiments of the invention, the additive ispresent in the electrochemical cell at concentrations typicallyassociated with catalysts. According to certain embodiments of theinvention, the additive is not completely consumed or reacted in theelectrochemical reaction in the cell. Preferably, the additive includedin the electrolyte catalyzes carbon-fluorine bond breakage and/orsolubilizes LiF. Generally, the additive can be anything thatcoordinates negative fluorine ion, although it is understood thatpreferable and exemplary additives are described herein.

In certain embodiments of the invention, the additive is present to theamount that is significantly lower than the amount of fluoride compoundpresent in the positive electrode of the electrochemical cell. Incertain embodiments of the invention, the additive is present at a molaramount that is at least about 10 times lower than the molar amount offluoride present in the positive electrode of the electrochemical cell.In certain embodiments of the invention, the additive is present at amolar amount that is at least about 100 times lower than the molaramount of fluoride compound present in the positive electrode of theelectrochemical cell. In certain embodiments of the invention, theadditive is present at a molar amount that is at least about 1000 timeslower than the molar amount of fluoride compound present in the positiveelectrode of the electrochemical cell.

In certain embodiments of the invention, the additive is present at anamount that is significantly lower than the amount of electrolyte saltpresent in the electrolyte solution of the electrochemical cell. Incertain embodiments of the invention, the concentration of additive inthe electronic solution is less than to equal to about 0.1 M, 0.09 M,0.08 M, 0.07 M, 0.06 M, 0.05 M, 0.04 M, 0.03 M, 0.02 M, or 0.01 M. Incertain embodiments of the invention, the concentration of additive inthe electrolyte solution is in the range of about 0.1 M to about 0.03 M.In certain embodiments of the invention, the concentration of additivein the electrolyte solution is about 0.03 M. In certain embodiments ofthe invention, the concentration of additive in the electrolyte solutionis in the range of about 0.03 M to about 0.01 M. In certain embodimentsof the invention, the concentration of additive in the electrolytesolution is in the range of about 0.01 M to about 0.001 M. In certainembodiments of the invention, the concentration of additive in theelectronic solution is less than to equal to about 0.01 M, 0.009 M,0.008 M, 0.007 M, 0.006 M, 0.005 M, 0.004 M, 0.003 M, 0.002 M, or 0.001M.

Development of the additives of certain embodiments of the inventionrequired a distinct approach from the design of previously knownelectrochemical cells. Certain additives in the novel electrochemicalcells described herein reversibly coordinate fluoride ions. In selectingand developing candidate materials for use as additives, certainfeatures and properties were identified. For example, candidatematerials were selected in order to modulate the comparative strength ofthe interaction between the additive and fluoride ions. Differentcandidate ligand materials were selected to be paired with differentcandidate central atom materials. These ligand-central atom pairs wereselected to form Lewis acid compounds of varying strengths of areversible interaction with fluoride ions.

Lewis acid additives of certain embodiments of the invention preferablyare stable under dry room conditions, reversibly coordinate fluoride,are catalytic, and do not include acidic protons.

In the design of previously known electrochemical cells,fluoride-containing additives have been used differently than has usedherein in certain embodiments of the invention. In such previouselectrochemical cells, the fluorine containing additives were used toreact with lithium-fluoride compounds to enable the use oflithium-fluoride compounds in an electrolyte salt. In such a reaction,the fluorine-containing additive was used stoichiometrically. That is,the fluorine-containing additive was reacted in equal amounts with thelithium-fluoride compound. In such previous reactions, the fluorinecoordinating additives irreversibly complex the fluoride ions in thefirst lithium-fluoride in order to form a second lithium-fluoridecompound. Thus, the goal of the previously known use of fluorinecontaining additives and electrochemical cells was to form a solubleelectrolyte salt by completely consuming the fluorine-coordinatingadditives in a stoichiometric reactions with lithium-fluoride.

According to certain embodiments of the invention, additives includetri-i-propylborate; triphenylboron; tris(trimethylsiloxy)boron;ethyl-2-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)benzoate;3-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)furan;triphenylphosphine; aluminum fluoride; trimethyl(phenyl)silane; boronfluoride; ethyl ether complex (47-48% boron fluoride);tris(pentafluorophenyl)boron; aluminum chloride; aluminum triflate;antimony(V) fluoride; zinc chloride; zinc fluoride; lanthanum(III)chloride; lanthanum(III) fluoride; 1,1,1-trifluoroacetone;1,3-bis[4-(dimethylamino)phenyl]-2,4-dihydroxycyclobutenediyliumdihydroxide; 2,3,5,6-tetrafluoro-7,7,8,8-tetracyanoquinodimethane;acetone; calcium trifluoromethanesulfonate; dimethylphosphinic chloride;hexafluorobenzene; lanthanum(III) trifluoromethanesulfonate; magnesiumtrifluoromethanesulfonate; potassium trifluoromethanesulfonate; sodiumtrifluoromethanesulfonate; tetramethylammonium tetrafluoroborate;tri-tert-butyl borate; triethylborate; yttrium(III)trifluoromethanesulfonate; and combinations thereof.

There are several contrasts between the previously known uses offluorine coordinating additives and the additives of certain embodimentsof the invention. For example, the additives of certain embodiments ofthe invention: are present in the electrochemical cell innon-stoichiometric amounts; are present in amounts typically associatedwith catalytic activity; or not consumed in a reaction to produce anelectrolyte salt; are not used as a reagent in a salt-forming reaction;reversibly complex fluoride ions; catalyze the breakage of chemicalbonds in the carbon-fluoride or the metal-fluoride compound present inthe electrochemical cell; at least partially dissolve a lithium-fluoridecompound present in the electrochemical cell; increase the mobility of alithium-fluoride compound present in the electrochemical cell; reducethe formation of large aggregates. It is understood that not alladditives of every embodiment of the invention exhibit all of the aboveproperties.

Development of the additives of other embodiments of the invention alsorequired a distinct approach from the use of compounds previously knownto catalyze carbon-fluorine bond breakage. In selecting and developingcandidate materials for use as additives, certain features andproperties were identified. For example, electron-rich transition metalcomplexes either have an open coordination site or the potential to giveup a ligand under the desired reaction conditions. In another example,the electron-rich transition metal complexes include bulky ligands,which may reduce the rate of side reactions during the desired reaction.

Electron-rich transition metal complexes preferably have one of thefollowing metal centers: scandium, titanium, vanadium, chromium,manganese, iron, cobalt, nickel, copper, yttrium, zirconium, molybdenum,ruthenium, rhodium, palladium, hafnium, rhenium, iridium, and gold.Electron-rich transition metal complexes preferably have one or more ofthe following chemical properties, structures, or moieties: low valency,high valency, a chelating ligand, a salt, a halogen, aromaticity,contain cyclopentadiene, contain a carbene, contain a phosphine, containa carbonyl, and/or is sterically congested.

According to certain embodiments of the invention, additives includepentamethylcyclopentadienylchromium dicarbonyl dimer;(1,10-phenanthroline)bis(triphenylphosphine)copper(I) nitratedichloromethane adduct; (1 R,2R)-(-)-1 ,2-cyclohexanediamino-N,N′-bis(3,5-di-t-butylsalicylidene)cobalt(II);(trimethyl)pentamethylcyclopentadienyltitanium(IV);[1,3-bis(2,4,6-trimethylphenyl)-2-imidazolidinylidene]-[2-[[(4-methylphenyl)imino]methyl]-4-nitrophenolyl]-[3-phenyl-1H-inden-1-ylidene]ruthenium(II) chloride;1,1′-bis(di-i-propylphosphino)ferrocene;1,1′-bis(di-t-butylphosphino)ferrocene;1,1′-bis(dicyclohexylphosphino)ferrocene;1,1‘-bis(diphenylphosphino)ferrocene;1,2-bis((2R,5R)-2,5-diethylphospholano)ethane(cyclooctadiene)rhodium(I)tetrafluoroborate; 3-di-i-propylphosphino-2-(N, N-dimethylamino)-1H-indene(1 ,5-cyclooctadiene)iridium(I) hexafluorophosphate; benzenechromium tricarbonyl; bis(2,4-dimethylpentadienyl)ruthenium (II);bis(cyclopentadienyl)iron; bis(cyclopentadienyl)manganese;bis(cyclopentadienyl)zirconium dichloride;bis(pentamethylcyclopentadienyl)cobalticinium hexafluorophosphate;bis[1,2-bis(diphenylphosphino)ethane]palladium (0);chloro(pentamethylcyclopentadienyl)[(2-pyridinyl-kN)phenyl-kC]iridum(III);chloro[1,3-bis(2,6-di-i-propylphenyl)imidazol-2-ylidene]copper(I);chlorotris(triphenylphosphine)cobalt(I); chromium(III)hexafluoroacetylacetonate; copper(I) acetate;cyclopentadienyl(triethylphosphine)copper(I); cyclopentadienylirondicarbonyl dimer; cyclopentadienylmanganese tricarbonyl;cyclopentadienylvanadium tetracarbonyl; dichloro(benzene)ruthenium(II)dimer; dichloro[1,1’-bis(diphenylphosphino)ferrocene]cobalt(II);dichloro[1,1′-bis(diphenylphosphino)ferrocene]nickel(II); iron(II)phthalocyanine; manganese(II) phthalocyanine; manganese(III)meso-tetraphenylporphine acetate; nickel(II) phthalocyanine;pentamethylcyclopentadienylmolybdenum dicarbonyl dimer;pentamethylcyclopentadienylrhenium tricarbonyl;pentamethylcyclopentadienyltitanium trimethoxide;tris(2,2,6,6-tetramethyl-3,5-heptanedionato)chromium(III);tris(2,2,6,6-tetramethyl-3,5-heptanedionato)scandium(III);tris(2,2,6,6-tetramethyl-3,5-heptanedionato)titanium(III);tris(cyclopentadienyl)yttrium; and combinations thereof.

In known uses of electron-rich transition metal catalysts to fluorinateand/or defluorinate organic molecules, the reactions occurred in theliquid phase and in the absence of strong reducing agents. In contrast,the materials and conditions in the electrochemical cells describedherein are different from the conditions of such known uses. The use ofthe additives according to certain embodiments in batteries addsconstraints beyond those required for a fluorination and/ordefluorination reaction of organic molecules.

As illustrated in certain examples herein, the additives of certainembodiments of the invention address some of the challenges of batteriesby enabling higher power, increasing operating voltage, increasingcapacity at a high discharge rate, producing heat generation, andincreasing heat dissipation. For example, in high-drain applicationscertain embodiments improve the energy capacity of batteries such that ahigher voltage may be achieved at a high current when compared to priorbatteries. Searching embodiments extend the useful life of batteriesunder moderate to high drain conditions. Unexpectedly, the additives ofcertain embodiments of the present invention address these challenges atlow concentrations.

Electrolyte solutions including additives of certain embodiments of theinvention were included in electrochemical cells according to certainexamples set forth below. In some situations, the CFx material in thecathode was coated using materials and method disclosed in copendingU.S. patent application Ser. No. 13/612,800 (Attorney Docket No.11006U503), which application is incorporated by reference herein in itsentirety. The combination of the electrolyte solutions includingadditives of certain embodiments of the invention and such coated CFxmaterials demonstrated improved performance. In many cases, theperformance improvements were substantially greater than the performanceimprovement realized by either the additive or the coating method on itsown.

The following examples describe specific aspects of some embodiments ofthe invention to illustrate and provide a description for those ofordinary skill in the art. The examples should not be construed aslimiting the invention, as the examples merely provide specificmethodology useful in understanding and practicing some embodiments ofthe invention.

EXAMPLES Fabrication of Electrochemical Cells Containing Additives

Materials and Synthetic Methods. All cells were prepared in a highpurity argon filled glovebox (M-Braun, oxygen and humidity contents wereless than 0.1 ppm). Unless otherwise specified, materials were obtainedfrom commercial sources (e.g., Sigma-Aldrich, Advanced ResearchChemicals Inc., Alfa Aesar) without further purification.

Electrode Formulation Summary. CFx was coated through a milling and/orannealing process. Milling vessels were loaded with CFx, carbonprecursor (PVDF) (5 wt. %), and solvents. The vessels were sealed andthen milled. After milling, solvents were evaporated at about 60 degreesC. and, if necessary, samples were annealed under flowing nitrogen gas.CFx/SVO hybrid electrodes were prepared with 50 wt. % SVO, 35 wt. %coated CFx, 4 wt. % carbon black, and 11 wt. % binder. For all theelectrodes, the solid components were (SVO, CFx and carbon) premixedwith mortar and pestle prior to preparing the formulation. Allelectrodes were prepared with a formulation composition of 85:11:4Active materials: Binder: Conductive additive according to the followingformulation method.

Electrode Preparation. About 200 mg PVDF (Sigma Aldrich) was dissolvedin 10mL NMP (Sigma Aldrich) overnight. In come cases, 72.7 mg ofconductive additive was added to the solution and allowed to stir forseveral hours. About 150 mg of premixed electrode solids were added to 1mL of this solution and stirred overnight. Films were cast by droppingabout 100 μL of slurry onto current collectors and drying at about 150degrees C. for about 1 hour. dried films were allowed to cool, and werethen pressed at 1 tons/cm². Electrodes were further dried at about 150°C. under vacuum for 12 hours before being brought into a glove box forbattery assembly. In some cases, a pure CFx electrode was prepared usingsimilar methods.

Electrochemical Characterization. Cells were made using lithium as ananode, Cellguard 2320 separator, and 180 μL of 1M LiAsF₆ in 1:1 PC : DMEas electrolyte. Electrodes and cells were electrochemicallycharacterized at 37° C. using the following protocols:

Characterization Protocols. (1) Constant current discharge at C/100. (2)Pulsed discharge: Cells were subject to a series of constant currentpulsing at about 20% depth of discharge. Each pulse measurement wasconducted as follows: a series of 4 consecutive pulses of 2 mA/cm² and30 second duration was applied with a 30 second rest separating thepulses. Battery voltage was monitored during the pulse sequence allowinginternal battery resistance and pulse power to be calculated. Prior toconducting a pulse measurement, the cell was discharged at C/100 to thedesired depth of discharge followed by holding at open current voltage(OCV) for 20 hours. (3) Alternate pulsed discharge: some cells were alsotested following the pulsed discharge protocol except using up to 25mA/cm² pulsing with 10 second duration and 10 second rest separating thepulses. (4) 0.01C background discharge with high current pulsing atpredefined depths of discharge for power measurements. Pulsing wascarried out at 5 mA/cm² for 10 seconds followed by 10 seconds of OCV.Pulsing was done in sets of four pulses and the cell rested at OCV forabout 10 hours prior to the first pulse and after the forth pulse. (5)testing on pure CFx electrodes was done by constant current discharge at1C and 0.1C rate.

Electrolyte Additive Screening. Electrodes were prepared for thestandard CFx/SVO hybrid electrode using unmodified CFx. All electrolyteadditives were added to 1M LiAsF₆ in 1:1 PC : DME.

Electrolyte additives were tested in concentrations of about 0.03, about0.1 and about 1.0 mol/L. table 1 lists the electrolyte additives usedfor primary screening.

Testing began with a primary screen of selected electrolyte additives.

TABLE 1 List of Electrolyte Additives and Shorthand Notation ElectrolyteCode Electrolyte Additive TiPB Tri-i-propylborate TPB TriphenylboronTMSB Tris(trimethylsiloxy)boron CB1 Ethyl-2-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)benzoate CB2 3-(4,4,5,5-Tetramethyl-1,3,2-dioxaborolan-2-yl)furan TPP Triphenylphosphine AlF3 Aluminum fluorideTMPS Trimethyl(phenyl)silane

Second Screen. Electrolyte additives were tested using about 0.03 mol/Lconcentration. Table 2 lists the electrolyte additives used forsecondary screening. In addition, several of the primary screenadditives were tested with high current (25 mA/cm²) pulsing.

TABLE 2 List of Electrolyte Additives and Short-Hand NotationElectrolyte Code Electrolyte Additive BF3 Boron fluoride, ethyl ethercomplex (47- 48% Boron fluoride) TPFPB Tris(pentafluorophenyl)boronAlCl3 Aluminum chloride Al(otf)3 Aluminum triflate SbF5 Antimony(V)fluoride ZnCl2 Zinc chloride ZnF2 Zinc fluoride LaCl3 Lanthanum(III)chloride LaF3 Lanthanum(III) fluoride

Testing of Electrochemical Cells Containing Additives

Electrochemical cells formed according to the above example were testedusing a variety of test methods. When compared to electrochemical cellswithout additives, certain electrochemical cells exhibited increases inperformance.

Third Screen. Table 3 lists the additives tested in a third screen ofadditives including Lewis acids and their performance in voltage andrate capability testing as compared to a control. Cells were fabricatedusing a hybrid cathode (CFx/SVO) for the results reported in Table 3.Rate capability is expressed as the percentage of the discharge at Crate as compared to 0.1 C rate.

TABLE 3 Performance of Lewis Acid Type Additives Voltage at 1 C RateCapability C/0.1 C Electrolyte Additive (V) (%) Control 2.27 76.001,1,1-Trifluoroacetone 2.30 82.73 1,3-Bis[4- 2.28 82.86(dimethylamino)phenyl]-2,4- dihydroxycyclobutenediylium dihydroxide2,3,5,6-Tetrafluoro-7,7,8,8- 2.26 83.43 tetracyanoquinodimethane Acetone2.26 81.82 Calcium 2.25 79.95 trifluoromethanesulfonateDimethylphosphinic chloride 2.30 85.10 Hexafluorobenzene 2.27 84.03Lanthanum(III) 2.24 79.62 trifluoromethanesulfonate Magnesium 2.28 78.36trifluoromethanesulfonate Potassium 2.28 84.43 trifluoromethanesulfonateSodium 2.27 80.72 trifluoromethanesulfonate Tetramethylammonium 2.2979.69 tetrafluoroborate Tri-tert-butyl borate 2.31 79.42 Triethylborate2.30 73.78 Yttrium(III) 2.26 81.69 trifluoromethanesulfonate

Table 4 lists the additives tested in a third screen of additivesincluding Lewis acids and their performance in testing as compared to acontrol. Cells were fabricated using a hybrid cathode (CFx/SVO) for theresults reported in Table 4. Table 4 reports the power measured for thecell at 70% depth of discharge and at 80% depth of discharge.

TABLE 4 Performance of Lewis Acid Type Additives Power Power 70%Capacity 80% Capacity Electrolyte Additive (mW/cm²) (mW/cm²) Control12.15 11.70 1,1,1-Trifluoroacetone 12.64 11.87 1,3-Bis[4- 12.27 11.73(dimethylamino)phenyl]-2,4- dihydroxycyclobutenediylium dihydroxide2,3,5,6-Tetrafluoro-7,7,8,8- 10.03 9.79 tetracyanoquinodimethane Acetone12.40 11.73 Calcium 11.75 11.39 trifluoromethanesulfonateDimethylphosphinic chloride 12.23 11.61 Hexafluorobenzene 12.45 11.82Lanthanum(III) 12.37 12.14 trifluoromethanesulfonate Magnesium 12.3111.74 trifluoromethanesulfonate Potassium 12.72 11.93trifluoromethanesulfonate Sodium 12.23 11.69 trifluoromethanesulfonateTetramethylammonium 12.64 11.97 tetrafluoroborate Tri-tert-butyl borate12.05 11.87 Triethylborate 12.57 12.07 Yttrium(III) 12.44 12.05trifluoromethanesulfonate

Transition Metal Catalyst Additives: Table 5 lists the additives testedin a screen of additives including transition metal and other electronrich materials and their performance in voltage and rate capabilitytesting as compared to a control. Cells were fabricated using a hybridcathode (CFx/SVO) for the results reported in Table 5. Rate capabilityis expressed as the percentage of the discharge at C rate as compared to0.1 C rate.

TABLE 5 Performance of Transition Metal Type Additives Voltage Rate atCapability 1 C C/0.1 C Electrolyte Additive (V) (%) Control 2.26 76.58Pentamethylcyclopentadienylchromium dicarbonyl 2.27 81.60 dimer (1,10-2.08 36.77 Phenanthroline)bis(triphenylphosphine)copper(I) nitratedichloromethane adduct (1R,2R)-(−)-1,2-Cyclohexanediamino-N,N′-bis(3,5-2.24 81.11 di-t-butylsalicylidene)cobalt(II)(Trimethyl)pentamethylcyclopenta- 2.12 62.63 dienyltitanium(IV)[1,3-Bis(2,4,6-trimethylphenyl)-2- 2.22 69.61imidazolidinylidene]-[2-[[(4- methylphenyl)imino]methyl]-4-nitrophenoly]-[3-phenyl-1H-inden-1- ylidene]ruthenium(II) chloride1,1′-Bis(di-i-propylphosphino)ferrocene 2.26 78.961,1′-Bis(di-t-butylphosphino)ferrocene 2.26 74.821,1′-Bis(dicyclohexylphosphino)ferrocene 2.29 77.761,1′-Bis(diphenylphosphino)ferrocene 2.24 81.431,2-Bis((2R,5R)-2,5-diethyl- 2.17 63.42phospholano)ethane(cyclooctadiene)rhodium(I) tetrafluoroborate3-Di-i-propylphosphino-2-(N,N-dimethylamino)-1H- 2.23 79.40indene(1,5-cyclooctadiene)iridium(I) hexafluorophosphate Benzenechromium tricarbonyl 2.29 82.25Bis(2,4-dimethylpentadienyl)ruthenium(II) 2.29 75.87Bis(cyclopentadienyl)iron 2.27 77.81 Bis(cyclopentadienyl)manganese 1.65 5.02 Bis(cyclopentadienyl)zirconium dichloride 2.09 44.36Bis(pentamethylcyclopentadienyl)cobalticinium 2.26 80.80hexafluorophosphate Bis[1,2-bis(diphenylphosphino)ethane]palladium (0)2.23 74.79 Chloro(pentamethylcyclopentadienyl)[(2-pyridinyl- 2.24 77.64kN)phenyl-kC]iridum(III)Chloro[1,3-bis(2,6-di-i-propylphenyl)imidazol-2- 2.30 83.68ylidene]copper(I) Chlorotris(triphenylphosphine)cobalt(I) 2.14 64.99Chromium(III) hexafluoroacetylacetonate 2.25 82.19 Copper(I) acetate2.27 84.78 Cyclopentadienyl(triethylphosphine)copper(I) 1.71 36.84Cyclopentadienyliron dicarbonyl dimer 2.27 84.40Cyclopentadienylmanganese tricarbonyl 2.22 80.83Cyclopentadienylvanadium tetracarbonyl 2.24 56.81Dichloro(benzene)ruthenium(II) dimer 2.24 77.84 Dichloro[1,1′- 2.2477.82 bis(diphenylphosphino)ferrocene]cobalt(II) Dichloro[1,1′- 2.2372.39 bis(diphenylphosphino)ferrocene]nickel(II) Iron(II) phthalocyanine2.33 54.65 Manganese(II) phthalocyanine No Data No Data Manganese(III)meso-tetraphenylporphine acetate 2.08 54.35 Nickel(II) phthalocyanine2.24 78.67 Pentamethylcyclopentadienylmolybdenum 2.28 81.42 dicarbonyldimer Pentamethylcyclopentadienylrhenium tricarbonyl 2.26 78.18Pentamethylcyclopentadienyltitanium trimethoxide 2.14 68.21Tris(2,2,6,6-tetramethyl-3,5- 2.28 76.65 heptanedionato)chromium(III)Tris(2,2,6,6-tetramethyl-3,5- 2.26 81.25 heptanedionato)scandium(III)Tris(2,2,6,6-tetramethyl-3,5- 2.17 69.79 heptanedionato)titanium(III)Tris(cyclopentadienyl)yttrium No Data No Data Vanadylmeso-tetraphenylporphine 2.27 76.19

Table 6 lists the additives tested in a screen of additives includingtransition metal and other electron rich materials and their performancein testing as compared to a control. Cells were fabricated using ahybrid cathode (CFx/SVO) for the results reported in Table 6. Table 6reports the power measured for the cell at 70% depth of discharge and at80% depth of discharge.

TABLE 6 Performance of Transition Metal Type Additives Power Power (70%(80% Capacity, Capacity, Electrolyte Additive mW/cm²) mW/cm²) Control12.15 11.70 Pentamethylcyclopentadienylchromium 12.36 11.97 dicarbonyldimer (1,10- 10.70 10.11 Phenanthroline)bis(triphenylphosphine)copper(I)nitrate dichloromethane adduct (1R,2R)-(−)-1,2-Cyclohexanediamino-N,N′-12.31 11.85 bis(3,5-di-t-butylsalicylidene)cobalt(II)(Trimethyl)pentamethylcyclopenta- 9.67 9.42 dienyltitanium(IV)[1,3-Bis(2,4,6-trimethylphenyl)-2- 11.83 10.01imidazolidinylidene]-[2-[[(4-methylphenyl)imino]methyl]-4-nitrophenoly]-[3-phenyl-1H-inden-1-ylidene]ruthenium(II) chloride1,1′-Bis(di-i-propylphosphino)ferrocene 12.04 11.431,1′-Bis(di-t-butylphosphino)ferrocene 12.30 11.671,1′-Bis(dicyclohexylphosphino)ferrocene 12.43 11.951,1′-Bis(diphenylphosphino)ferrocene 11.95 10.72 1,2-Bis((2R,5R)-2,5-11.53 10.82 diethylphospholano)ethane(cyclo- octadiene)rhodium(I)tetrafluoroborate 3-Di-i-propylphosphino-2-(N,N-dimethylamino)- 12.3611.93 1H-indene(1,5-cyclooctadiene)iridium(I) hexafluorophosphateBenzene chromium tricarbonyl 12.27 11.81Bis(2,4-dimethylpentadienyl)ruthenium(II) 11.97 11.46Bis(cyclopentadienyl)iron 12.13 11.72 Bis(cyclopentadienyl)manganese11.27 11.24 Bis(cyclopentadienyl)zirconium dichloride 12.04 11.34Bis(pentamethylcyclopentadienyl)cobalticinium 11.49 10.94hexafluorophosphate Bis[1,2-bis(diphenylphosphino)ethane]palladium 12.2511.34 (0) Chloro(pentamethylcyclopentadienyl)[(2- 11.53 10.93pyridinyl-kN)phenyl-kC]iridum(III)Chloro[1,3-bis(2,6-di-i-propylphenyl)imidazol-2- 12.25 11.96ylidene]copper(I) Chlorotris(triphenylphosphine)cobalt(I) 10.57 9.00Chromium(III) hexafluoroacetylacetonate 12.07 11.64 Copper(I) acetate12.15 11.57 Cyclopentadienyl(triethylphosphine)copper(I) 9.00 7.86Cyclopentadienyliron dicarbonyl dimer 12.20 11.48Cyclopentadienylmanganese tricarbonyl 11.94 11.61Cyclopentadienylvanadium tetracarbonyl 12.14 11.77Dichloro(benzene)ruthenium(II) dimer 5.15 4.29 Dichloro[1,1′- 9.91 7.90bis(diphenylphosphino)ferrocene]cobalt(II) Dichloro[1,1′- 10.13 8.33bis(diphenylphosphino)ferrocene]nickel(II) Iron(II) phthalocyanine 11.8111.43 Manganese(II) phthalocyanine 11.41 11.05 Manganese(III)meso-tetraphenylporphine acetate 12.05 9.80 Nickel(II) phthalocyanine12.31 11.90 Pentamethylcyclopentadienylmolybdenum 12.09 11.68 dicarbonyldimer Pentamethylcyclopentadienylrhenium 11.83 11.49 tricarbonylPentamethylcyclopentadienyltitanium 11.48 11.05 trimethoxideTris(2,2,6,6-tetramethyl-3,5- 12.26 11.82 heptanedionato)chromium(III)Tris(2,2,6,6-tetramethyl-3,5- 12.50 12.06 heptanedionato)scandium(III)Tris(2,2,6,6-tetramethyl-3,5- 12.34 11.95 heptanedionato)titanium(III)Tris(cyclopentadienyl)yttrium 12.25 11.84 Vanadylmeso-tetraphenylporphine 12.18 11.83

Table 7 lists the additives tested in a screen of additives includingtransition metal and other electron rich materials and their performancein voltage and rate capability testing as compared to a control. Cellswere fabricated using a pure CFx cathode for the results reported inTable 7. Rate capability is expressed as the percentage of the dischargeat C rate as compared to 0.1 C rate.

TABLE 7 Performance of Transition Metal Type Additives Rate Voltage atCapability 1 C C/0.1 C Electrolyte Additive (V) (%) Control 2.16 60.50Pentamethylcyclopentadienylchromium 2.24 62.89 dicarbonyl dimer (1,10-2.12 56.03 Phenanthroline)bis(triphenylphosphine)copper(I) nitratedichloromethane adduct (1R,2R)-(−)-1,2-Cyclohexanediamino-N,N′- 2.1967.02 bis(3,5-di-t-butylsalicylidene)cobalt(II)(Trimethyl)pentamethylcyclopentadienyl- 2.20 61.36 titanium(IV)[1,3-Bis(2,4,6-trimethylphenyl)-2- 2.14 55.64imidazolidinylidene]-[2-[[(4-methylphenyl)imino]methyl]-4-nitrophenolyl]-[3-phenyl-1H-inden-1-ylidene]ruthenium(II) chloride1,1′-Bis(di-i-propylphosphino)ferrocene 2.19 59.461,1′-Bis(di-t-butylphosphino)ferrocene 2.21 63.381,1′-Bis(dicyclohexylphosphino)ferrocene 2.18 55.371,1′-Bis(diphenylphosphino)ferrocene 2.23 65.16 1,2-Bis((2R,5R)-2,5-2.10 39.44 diethylphospholano)ethane(cyclo- octadiene)rhodium(I)tetrafluoroborate 3-Di-i-propylphosphino-2-(N,N-dimethylamino)- 2.1564.95 1H-indene(1,5-cyclooctadiene)iridium(I) hexafluorophosphateBenzene chromium tricarbonyl 2.14 42.95Bis(2,4-dimethylpentadienyl)ruthenium(II) 2.17 52.47Bis(cyclopentadienyl)iron 2.21 64.39 Bis(cyclopentadienyl)manganese 1.224.92 Bis(cyclopentadienyl)zirconium dichloride 2.10 43.32Bis(pentamethylcyclopentadienyl)cobalticinium 2.17 63.45hexafluorophosphate Bis[1,2-bis(diphenylphosphino)ethane]palladium 2.1748.35 (0) Chloro(pentamethylcyclopentadienyl)[(2- 2.12 56.42pyridinyl-kN)phenyl-kC]iridum(III)Chloro[1,3-bis(2,6-di-i-propylphenyl)imidazol-2- 2.20 62.34ylidene]copper(I) Chlorotris(triphenylphosphine)cobalt(I) 2.22 69.13Chromium(III) hexafluoroacetylacetonate 2.19 64.64 Copper(I) acetate2.23 64.38 Cyclopentadienyl(triethylphosphine)copper(I) 2.14 37.15Cyclopentadienyliron dicarbonyl dimer 2.15 64.21Cyclopentadienylmanganese tricarbonyl 2.13 47.52Cyclopentadienylvanadium tetracarbonyl 2.22 40.91Dichloro(benzene)ruthenium(II) dimer 2.07 31.84 Dichloro[1,1′- 2.1756.84 bis(diphenylphosphino)ferrocene]cobalt(II) Dichloro[1,1′- 2.1560.38 bis(diphenylphosphino)ferrocene]nickel(II) Iron(II) phthalocyanine2.11 49.52 Manganese(II) phthalocyanine 2.14 61.76 Manganese(III)meso-tetraphenylporphine acetate 2.12 46.32 Nickel(II) phthalocyanine2.11 40.15 Pentamethylcyclopentadienylmolybdenum 2.18 63.87 dicarbonyldimer Pentamethylcyclopentadienylrhenium tricarbonyl 2.15 54.05Pentamethylcyclopentadienyltitanium 2.21 57.04 trimethoxideTris(2,2,6,6-tetramethyl-3,5- 2.23 67.05 heptanedionato)chromium(III)Tris(2,2,6,6-tetramethyl-3,5- 2.21 62.21 heptanedionato)scandium(III)Tris(2,2,6,6-tetramethyl-3,5- 2.28 66.13 heptanedionato)titanium(III)Tris(cyclopentadienyl)yttrium 2.19 58.41 Vanadylmeso-tetraphenylporphine 2.21 52.99

Referring now to FIGS. 1A and 1B, the presence of certain additivesresulted in up to about 50 mV increases in open circuit voltage in aCFx/SVO hybrid cell. As depicted in FIGS. 1A and 1B, the presence ofcertain additives did not cause a reduction in operating voltage fromabout 20% to about 80% depth of discharge (DoD) in a CFx/SVO hybridcell. As depicted in FIGS. 2 and 3, the presence of certain additivesresulted in about a 0.1 mW/cm² increase impulse power at 2 mA/cm² pulsecurrent in a CFx/SVO hybrid cell. As depicted in FIG. 4, the presence ofcertain additives resulted in as much as about a 2 mW/cm² increaseimpulse power at 25 mA/cm² pulse current in a CFx/SVO hybrid cell.

Referring now to FIG. 5, certain additives improved the pulse power at80% depth of discharge. FIG. 6 illustrates the pulse power improvementat 80% depth of discharge. FIG. 7 shows voltage improvement from theseadditives for the pure CFx electrode.

Lewis acid additives according to certain embodiments improve ratecapability by about 6% as compared to control electrolyte withoutadditives. Lewis acid additives according to certain embodiments improvepulse power by about 5% as compared to control electrolyte withoutadditives. Lewis acid additives according to certain embodiments improveuseable capacity by about 14% as compared to control electrolyte withoutadditives.

Electron rich additives according to certain embodiments improve 1 Cvoltage by about 5.5% as compared to control electrolyte withoutadditives in cells with a pure CFx cathode. Electron rich additivesaccording to certain embodiments improve rate capability by about 14% ascompared to control electrolyte without additives in cells with a pureCFx cathode. Electron rich additives according to certain embodimentsimprove useable capacity by about 11% as compared to control electrolytewithout additives in cells with a hybrid cathode.

While the invention has been described with reference to the specificembodiments thereof, it should be understood by those skilled in the artthat various changes may be made and equivalents may be substitutedwithout departing from the true spirit and scope of the invention asdefined by the appended claims. In addition, many modifications may bemade to adapt a particular situation, material, composition of matter,method, or process to the objective, spirit and scope of the invention.All such modifications are intended to be within the scope of the claimsappended hereto. In particular, while the methods disclosed herein havebeen described with reference to particular operations performed in aparticular order, it will be understood that these operations may becombined, sub-divided, or re-ordered to form an equivalent methodwithout departing from the teachings of the invention. Accordingly,unless specifically indicated herein, the order and grouping of theoperations are not limitations of the invention.

1. An electrochemical cell, comprising: a positive electrode comprisinga first fluoride compound, the positive electrode producing a secondfluoride compound upon discharge; a negative electrode; an electrolytesolution comprising an additive having a borate group. 2-7. (canceled)8. The electrochemical cell of claim 1 wherein the ratio of the amountof additive in the electrochemical cell to the amount of first fluoridecompound in the electrochemical cell is less than about 0.1.
 9. Theelectrochemical cell of claim 1 wherein the additive reduces theformation of aggregates of the second fluoride compound.
 10. Theelectrochemical cell of claim 1 wherein the additive reversiblycoordinates fluoride ions.
 11. The electrochemical cell of claim 1wherein the additive catalyzes the breakage of chemical bonds in thefirst fluoride compound.
 12. The electrochemical cell of claim 1 whereinthe additive is present in the electrolyte solution at concentrations ofless than about 0.1 mol/L.
 13. A method of making an electrolytesolution, comprising: mixing a lithium salt, an organic solvent, and anadditive wherein the additive comprises a borate group.
 14. The methodof claim 13 wherein the additive is present in the electrolyte solutionat a concentration of less than about 0.1 mol/L. 15-17. (canceled)
 18. Aelectrolyte solution, comprising: a lithium salt, an organic solvent,and an additive, the additive characterized by not being substantiallyconsumed during charge and discharge cycles of an electrochemical cellcontaining the electrolyte solution; wherein the additive includes aborate group.
 19. The electrolyte solution of claim 18 wherein theadditive is selected from the group consisting of tri-tertbutyl borate,triethylborate, and tetramethylammonium tetrafluoroborate. 20.(canceled)
 21. The electrochemical cell of claim 1 wherein the additiveis selected from the group consisting of tri-tertbutyl borate,triethylborate, and tetramethylammonium tetrafluoroborate.
 22. Themethod of claim 13 wherein the additive is selected from the groupconsisting of tri-tertbutyl borate, triethylborate, andtetramethylammonium tetrafluoroborate.
 23. The electrolyte solution ofclaim 18 wherein the additive comprises tri-tertbutyl borate.
 24. Theelectrolyte solution of claim 18 wherein the additive comprisestriethylborate.
 25. The electrolyte solution of claim 18 wherein theadditive comprises tetramethylammonium tetrafluoroborate.